The guide to mast rake is “add three inches”
For instance when you put the tape up the mast for a Plus S you set it at 19′ 3″ to the top of the black band at the gooseneck, fix it, and then take it to the transom where it should be 23′ 5″ to 23′ 7″ depending on conditions. More upright for light winds, raked further back for stronger winds. For the Hartley the measurement to the transom is 23′ 8″ to 23′ 10″.
Hope this helps.